CN104176114B - Steering control device and steering speed detection method - Google Patents

Abstract

The invention provides a steering control device and a steering speed detection method to obtain a steering speed without offset error. The method includes: obtaining the first steering speed based on the detection value of the current from the current sensor (9) and the voltage from the voltage sensor (10), calculating a correction value of the first steering speed based on the detection value of the steering angle, and using the correction value a steering speed calculation unit (12) that corrects the first steering speed and outputs it as a steering speed; a first unit that obtains a first steering assist torque for returning the steering system to a neutral position based on the steering speed; A steering assist torque calculation unit (15): a second steering assist torque calculation for obtaining a second steering assist torque for assisting the driver's steering based on the driver's steering torque from the torque sensor 5 part (17); and a current driver (19) for driving the electric motor based on the first and second steering assist torques.

Description

Steering control device and steering speed detection method

technical field

The present invention relates to a steering control device and a steering speed detection method, in particular to a steering control device and a steering speed detection method for assisting a driver's steering.

Background technique

In a conventional electric power steering apparatus, an electric motor is provided for providing torque to a steering system (a steering wheel of a vehicle) in order to assist a driver's operation. In a conventional electric power steering apparatus, a driver's steering speed is detected using a voltage between terminals of a motor (for example, refer to Patent Documents 1 and 2).

Patent Document 1 describes an electric power steering device that obtains a motor angular velocity based on a voltage between terminals of a motor.

Patent Document 2 describes an electric power steering device that detects a steering speed based on electric current and voltage of a motor. In Patent Document 2, the offset error of the detected steering speed is eliminated by using a high-pass filter.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2001-171533

Patent Document 2: Japanese Patent Laid-Open No. 2001-278083

Contents of the invention

The technical problem to be solved by the invention

Patent Document 1 describes detecting the angular velocity of the motor using the voltage between the terminals of the motor, but does not consider that the voltage between the terminals of the motor includes an offset error. Therefore, there is a problem that, when the voltage between the terminals of the motor includes an offset error, the detected steering speed also includes an offset error.

Patent Document 2 describes using a high-pass filter to eliminate the offset error of the steering speed, but there is a problem that low-frequency components of the steering speed are also eliminated by the high-pass filter.

The present invention was made to solve the above problems, and an object of the present invention is to obtain a steering control device and a steering speed detection method capable of obtaining a steering speed free of offset errors.

Technical solutions adopted to solve technical problems

The steering control device of the present invention includes: a steering angle information acquiring unit that acquires information related to a steering angle of a steering system of a vehicle; a steering speed information acquiring unit that acquires information related to the steering angle first information on the steering speed of the system; and a correcting unit that, based on the information on the steering angle acquired by the steering angle information acquiring unit, corrects the steering speed information acquired by the steering speed information acquiring unit. The first information on the steering speed is corrected to obtain second information on the steering speed of the steering system.

Invention effect

The steering control device of the present invention includes: a steering angle information acquiring unit that acquires information related to a steering angle of a steering system of a vehicle; a steering speed information acquiring unit that acquires information related to the steering angle first information on the steering speed of the system; and a correcting unit that, based on the information on the steering angle acquired by the steering angle information acquiring unit, corrects the steering speed information acquired by the steering speed information acquiring unit. The first information on the steering speed is corrected to obtain the second information on the steering speed of the steering system, so that a steering speed that does not include an offset error can be obtained.

Description of drawings

FIG. 1 is a block diagram showing a steering control device and its surroundings according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing the configuration of a steering control device according to Embodiment 1 of the present invention.

3 is a flowchart showing the operation of the steering control device according to Embodiment 1 of the present invention.

4 is a flowchart showing the operation of a steering speed calculation unit of the steering control device according to Embodiment 2 of the present invention.

5 is a block diagram showing a part of the internal configuration of a steering speed calculation unit of the steering control device according to Embodiment 2 of the present invention.

6 is a block diagram showing part of a modified example of the internal configuration of a steering speed calculation unit of the steering control device according to Embodiment 2 of the present invention.

FIG. 7 is a diagram showing effects of the steering control device according to Embodiment 2 of the present invention.

8 is a flowchart showing the operation of a steering speed calculation unit of the steering control device according to Embodiment 3 of the present invention.

9 is a block diagram showing part of the internal configuration of a steering speed calculation unit of the steering control device according to Embodiment 3 of the present invention.

detailed description

Implementation mode 1.

FIG. 1 is a block diagram showing a steering control device and its surroundings according to Embodiment 1 of the present invention. Steering control devices are installed in vehicles such as automobiles. The vehicle is provided with two front wheels (steering wheels 3 ) and two rear wheels (drive wheels) (not shown). As shown in FIG. 1 , a steering system for a driver to operate, that is, a steering wheel 1 (steering wheel) is provided in a vehicle. The steering wheel 1 is connected to the steering shaft 2 . Furthermore, the steering shaft 2 is connected to two steering wheels 3 . When the driver turns the steering wheel 1 , the left and right steering wheels 3 are steered according to the rotation of the steering shaft 2 . A steering angle sensor 4 for detecting a steering angle is arranged on the steering wheel 1 . A torque sensor 5 is arranged on the steering shaft 2 . The torque sensor 5 detects the steering torque acting on the steering shaft 2 . Furthermore, the electric motor 6 is connected to the steering shaft 2 via the reduction mechanism 7 . The steering assist torque generated by the electric motor 6 is supplied to the steering shaft 2 . The vehicle speed of the vehicle is detected by a vehicle speed sensor 8 . In addition, a current flowing through the motor 6 (hereinafter referred to as a motor current) is detected by a current sensor 6 . A voltage between terminals of the motor 6 (hereinafter referred to as a motor voltage) is detected by a voltage sensor 10 .

Here, the steering angle sensor 4 constitutes a steering angle information acquisition unit that acquires information on the steering angle of the steering system of the vehicle. However, it is not limited to this case, and the steering angle information acquisition unit that acquires information on the steering angle of the vehicle's steering system only needs to be able to acquire information on the steering angle of the vehicle's steering system. The configuration of the flight rate sensor. The yaw rate sensor is a sensor that detects a yaw rate (speed of change in a turning angle of the vehicle in a turning direction).

Detection values of the steering angle sensor 4 , the torque sensor 5 , the vehicle speed sensor 8 , the current sensor 9 , and the voltage sensor 10 are input to the control unit 11 . The control unit 11 calculates a target steering assist torque to be generated by the electric motor 6 based on these detection values, and controls the value of the current to be supplied to the electric motor 6 based on the target steering assist torque.

FIG. 2 is a diagram showing the configuration of the steering control device according to Embodiment 1. FIG. As shown in FIG. 2 , the steering control device is composed of a plurality of sensors including a steering angle sensor 4 , a torque sensor 5 , a vehicle speed sensor 8 , a current sensor 9 , and a voltage sensor 10 , and a control unit 11 . As shown in Figure 2, control unit 11 is made up of computing device 40 and current driver 19, and this computing device 40 is made up of microcomputer, and this microcomputer is provided with memory (not shown) including ROM and RAM, and this current driver 19 is made up of to The electric motor 6 supplies electric current to drive the electric motor 6 .

In addition, in Embodiment 1, a description will be given taking, as an example, a steering control device that includes control that assists the driver's steering (hereinafter referred to as steering assist control) Control for returning the steering wheel 1 to the neutral position even in a region where the steering wheel 1 has not returned to the neutral position due to a small torque (hereinafter referred to as steering wheel return control).

As shown in FIG. 2 , the calculation unit 40 is provided with a steering speed calculation unit 12, a fixed steering determination unit 13, a target steering speed setting unit 14, a first steering assist torque calculation unit 15, a steering state determination unit 16, a second Steering assist torque calculating unit 17 and adding unit 18 .

Steering speed calculation unit 12 receives detection values from steering angle sensor 4 , current sensor 9 , and voltage sensor 10 , and calculates a steering speed based on these detection values. Steering speed calculation unit 12 acquires a motor current from current sensor 9 and a motor voltage from voltage sensor 10 . The steering speed calculation unit 12 obtains the induced voltage of the motor 6 from the motor current and the motor voltage. The calculation method of the induced voltage is described in the second embodiment. Next, the steering speed calculation unit 12 estimates the steering speed based on the induced voltage. However, this estimated steering speed includes an offset error due to oxide film at the contact portion, aging, and the like. Therefore, the steering speed calculation unit 12 obtains a correction value for correcting the estimated steering speed based on the steering angle acquired from the steering angle sensor 4 . The steering speed calculation unit 12 corrects the estimated steering speed using the correction value, and outputs the corrected steering speed.

Here, the steering speed computing unit 12 constitutes a steering speed information acquiring unit that acquires first information on the steering speed of the steering system, and a steering angle information acquiring unit (steering angle sensor or yaw rate sensor) based on the steering angle information acquiring unit (steering angle sensor or yaw rate sensor). A correcting unit that corrects the first information acquired by the steering speed information acquisition unit and acquires second information related to the steering speed of the steering system. Here, as the first information related to the steering speed of the steering system, the induced voltage of the electric motor 6 is exemplified, but it is not limited to this case. information. Note that the detailed operation of the operation speed calculation unit 12 will be described in Embodiments 2 and 3 described later.

The fixed steering determination unit 13 determines whether the steering system of the vehicle is in the fixed steering state. That is, the fixed steering determination unit 13 determines whether or not the steering wheel 1 is maintained at a substantially constant steering angle. The fixed steering determination unit 13 uses the steering speed calculated by the steering speed calculation unit 12 , and when the steering speed is less than a threshold value, determines that it is a “fixed steering state”, and outputs the current steering speed. On the other hand, when the steering speed is equal to or greater than the threshold value, it is determined that the vehicle is in a "non-fixed steering state", and the output steering angle is not updated, but the steering angle at the time of the previous determination that the steering was fixed is output.

The target steering speed setting unit 14 receives the steering angle from the steering angle sensor 4 , the vehicle speed from the vehicle speed sensor 8 , and the steering angle from the fixed steering determination unit 13 . The target steering speed setting unit 14 calculates the target steering speed based on these values. As a calculation method, for example, a lookup table that stores target steering speeds corresponding to these values may be stored in advance, and the steering angle from the steering angle sensor 4, the vehicle speed from the vehicle speed sensor 8, and the steering angle from the fixed steering determination unit may be input to the lookup table. 13 to obtain the corresponding target steering speed. Alternatively, an arithmetic expression for obtaining the target steering speed may be stored in advance, and the steering angle from the steering angle sensor 4, the vehicle speed from the vehicle speed sensor 8, and the steering angle from the fixed steering determination unit 13 may be input to the arithmetic expression to obtain Target turning speed.

The first steering assist torque calculation unit 15 receives the steering speed calculated by the steering speed calculation unit 12 and the target steering speed calculated by the target steering speed setting unit 14 as input. The first steering assist torque calculation unit 15 obtains a deviation between the steering speed and the target steering speed, and calculates the first steering assist torque based on the deviation. The first steering assist torque is a torque for returning the steering wheel 1 to the neutral position. In addition, as for the calculation method of the first steering assist torque, it is only necessary to store in advance a look-up table that stores the value of the first steering assist torque corresponding to the deviation between the steering speed and the target steering speed, and input the deviation value into the look-up table. It is only necessary to obtain the value of the corresponding first steering assist torque. Alternatively, an arithmetic expression for obtaining the first steering assist torque from a deviation between the steering speed and the target steering speed may be stored in advance, and the deviation value may be input to the arithmetic expression to obtain the first steering assist torque.

The first steering assist torque calculated by the first steering assist torque calculating unit 15 is input to the steering state determination unit 16 . The steering state determination unit 16 determines whether or not the first steering assist torque calculated by the first steering assist torque calculation unit 15 is necessary, and outputs the first steering assist torque when determined to be necessary, and outputs 0 when determined not to be necessary. Here, whether the driver releases the steering wheel is determined based on the steering torque from the torque sensor 5 . In this embodiment, the determination of whether to be in the released state is described as an example: when the detection value (absolute value) of the torque sensor 5 is above the threshold value, it is determined as the steering state, and when it is less than the threshold value, it is determined as the released state.

The steering torque from the torque sensor 5 is input to the second steering assist torque calculation unit 17 . The second steering assist torque calculation unit 17 calculates a second steering assist torque for assisting the driver's steering based on the steering torque. In addition, as for the calculation method of the second steering assist torque, it is only necessary to store in advance a lookup table storing the value of the second steering assist torque corresponding to the steering torque, and input the value of the steering torque into the lookup table, thereby It is only necessary to obtain the corresponding value of the second steering assist torque according to the look-up table. Alternatively, an arithmetic expression for obtaining the second steering assist torque from the steering torque may be stored in advance, and the value of the steering torque may be input to the arithmetic expression to obtain the second steering assist torque.

The addition unit 18 receives the output value from the steering state determination unit 16 (that is, the first steering assist torque from the first steering assist torque calculation unit 15 or 0), and the output value from the second steering assist torque calculation unit 17 . of the second steering assist torque. The adding unit 18 adds the output value from the steering state determining unit 16 to the second steering assist torque to calculate the final steering assist torque.

The current driver 19 supplies a current based on the steering assist torque obtained by the adder 18 to the electric motor 6 to drive the electric motor 6 . As a result, the electric motor 6 generates required steering assist torque.

Next, the operation of the steering control device according to Embodiment 1 will be described. FIG. 3 is a flowchart showing the operation of the steering control device according to the first embodiment. In addition, the operation|movement of FIG. 3 is repeatedly performed every control cycle.

First, in step S1, the control unit 11 acquires the steering angle from the steering angle sensor 4, the motor voltage from the voltage sensor 10, the motor current from the current sensor 9, the driver's steering torque from the torque sensor 5, and the vehicle speed The sensor 8 acquires the vehicle speed.

In step S2, first, the steering speed calculation unit 12 obtains the induced voltage from the motor current and the motor voltage. Next, the steering speed calculation unit 12 calculates the steering speed using the steering angle and the induced voltage, and outputs the steering speed.

In step S3 , the fixed steering determination unit 13 determines whether the steering system of the vehicle is in the fixed steering state, and if determined to be in the fixed steering state, outputs the current steering angle. On the other hand, when it is determined that the steering state is not fixed, the steering angle is not updated, and the steering angle at the time when it was determined that the steering was fixed last time is output.

In step S4, target steering speed setting unit 14 calculates a target steering speed based on the steering angle and vehicle speed acquired in step S1 and the steering angle acquired in step S3, and sets the target steering speed.

In step S5, the first steering assist torque calculation unit 15 calculates the first steering assist torque based on the target steering speed and the deviation of the steering speed.

In step S6, the steering state determination unit 16 determines whether the first steering assist torque calculated by the first steering assist torque calculation unit 15 is necessary, and outputs the first steering assist torque if determined to be necessary, and outputs the first steering assist torque when determined not to be necessary. Output 0 when required. Here, as the determination of whether it is necessary, it is determined whether the driver releases the steering wheel based on the steering torque from the torque sensor 5. If the steering wheel is released, the first steering assist torque is output, and if the steering wheel is not released, the output is 0 as the first steering assist torque.

In step S7, the second steering assist torque calculation unit 17 calculates a second steering assist torque for assisting the driver's steering based on the steering torque acquired in step S1.

In step S8, the adding unit 18 adds the first steering assist torque output from the steering state determination unit 16 and the second steering assist torque output from the second steering assist torque computing unit 17 to obtain the final steering assist torque. moment to output.

In step S9, the current driver 19 supplies current to the electric motor 6 based on the final steering assist torque obtained in step S8, thereby driving the electric motor 6.

The steering wheel return control in such a steering control device as described above determines a fixed steering state based on the steering speed and a threshold value. Therefore, when there is an offset error in the steering speed, or the resolution is low, it may be misjudged as a fixed steering. In addition, the first steering assist torque for returning the steering wheel 1 to the neutral position generates a steering assist torque such that the steering speed follows a change in the target steering speed. Therefore, when the steering assist torque contains an offset error, an appropriate steering assist torque may not be obtained, resulting in deterioration of the steering wheel return feeling. Therefore, in the first embodiment, by applying the steering speed calculation processing described in the second and third embodiments described below to the steering speed calculation unit 12, high response and high resolution can be obtained, and the offset error can be reduced. suppressed steering speed, and can obtain a suitable steering wheel return tactile feeling corresponding to the target steering speed.

As described above, in Embodiment 1, the steering control device includes: a steering angle information acquisition unit that acquires information on the steering angle of the steering system of the vehicle; a steering speed that acquires first information on the steering speed of the steering system; an information acquisition unit; based on the above-mentioned information related to the steering angle acquired by the steering angle information acquisition unit, correcting the first information related to the steering speed acquired by the steering speed information acquisition unit, and acquiring a steering angle related to the above-mentioned steering system. The correcting unit for the second information about the speed uses the information about the steering angle to correct the first information about the steering speed that includes an offset error, so that the first information about the steering speed that does not include an offset error can be obtained. second information.

Especially in the embodiment shown in Fig. 2, include: the steering angle sensor 4 that detects the steering angle of the steering wheel 1 of the steering system of the vehicle; ) current sensor 9; voltage sensor 10 for detecting the voltage between the terminals of the motor 6 (motor voltage); based on the steering angle detected by the steering angle sensor 4, the current detected by the current sensor 9, and the current detected by the voltage sensor 10 Voltage, to obtain the steering speed of the steering system steering speed calculation unit 12; based on the steering speed of the steering system obtained by the steering speed calculation unit 12 to calculate the steering assist torque, and use it as the first steering assist torque The first steering assist torque calculation unit 15 for output; and the current driver 19 for driving the electric motor 6 based on the first steering assist torque. The steering speed calculation unit 12 estimates the steering speed as the first steering speed based on the current and voltage. (the first information related to the steering speed), and calculate the correction value (information related to the steering angle) for correcting the first steering speed based on the steering angle, and use the above correction value to correct the first steering speed, to This is output as the steering speed of the steering system (second information on the steering speed). With this configuration, in Embodiment 1, the first steering speed (first information about steering speed) including an offset error is corrected using a correction value (information about steering angle) obtained from the steering angle. , so the steering speed (the second information about the steering speed) that does not contain an offset error can be obtained.

Furthermore, in Embodiment 1, the induced voltage of the motor 6 is obtained based on the current detected by the current sensor 9 and the voltage detected by the voltage sensor 10, and the first steering speed (related to the steering speed) is obtained based on the induced voltage. first information). Thus, a high-resolution steering speed can be obtained.

In addition, Embodiment 1 further includes: a torque sensor 5 arranged in the steering system to detect the steering torque of the steering system; and calculating the second The second steering assist torque calculation unit 17 of the steering assist torque, the current driver 19 drives the electric motor 6 based on the added value obtained by summing the first steering assist torque and the second steering assist torque by the adding unit 18 . Thus, the steering assist torque can be calculated using both the first steering assist torque for returning the steering wheel 1 to the neutral position and the second steering assist torque for assisting the driver's steering, Therefore, two types of control, the steering return control and the steering assist control, can be performed.

Implementation mode 2.

In Embodiment 2, the calculation of the steering speed executed by the steering speed calculation unit 12 provided in the control unit 11 will be described using the flowchart of FIG. 4 . That is, the flowchart of FIG. 4 is a diagram showing in detail the processing of step S2 of the flowchart of FIG. 3 .

Since the overall structure and operation of the steering control device according to Embodiment 2 are the same as those in Embodiment 1 described above, description thereof will be omitted here. In addition, the same code|symbol is used for the structure common to Embodiment 1 mentioned above, and the difference from Embodiment 1 will be mainly demonstrated below.

As shown in FIG. 4, first, in step S11, the steering speed calculation unit 12 uses the motor voltage EM from the voltage sensor 10 and the motor current IM from the current sensor 9 to obtain the induced voltage EE of the electric motor 6 corresponding to the steering speed. .

Here, the induced voltage EE of the motor 6 is obtained by the following equation (1) using the motor voltage EM and the motor current IM.

EE＝EM-IM·RM-Eb (1)

Here, let RM be the armature resistance of the motor 6 , and Eb be the drop voltage of the brush of the motor 6 .

Next, in step S12, the motor rotational speed VM is calculated from the induced voltage EE using the following equation (2).

VM=EE/Kp (2)

Here, Kp is the induced voltage coefficient.

Next, in step S13, the steering speed θ _omega is estimated from the motor rotation speed VM. In addition, the motor rotation speed and the steering speed have a relationship based on structural mechanisms such as a reduction gear, a steering wheel, a rack and a pinion of a tire shaft, and the like. In other words, motor speed is proportional to steering speed. Therefore, the estimated steering speed θ _omega is obtained from the following equation (3) based on the motor rotation speed. In addition, since the motor rotational speed is obtained based on the induced voltage, the estimated steering speed θ _omega is hereinafter referred to as "estimated steering speed based on the induced voltage" (first steering speed).

θ _omega = G _gear × VM (3)

Here, G _gear is a proportionality factor determined by the above-mentioned structural mechanism.

Here, since the dropout voltage Eb of the brush of the motor 6 changes due to influences such as contact oxide films and aging, the induced voltage EE includes these changes as offset errors. Accordingly, the steering speed θ _omega estimated from the induced voltage EE also includes an offset error.

Therefore, in step S14, the steering speed calculation unit 12 corrects the steering speed θ _omega using the information obtained from the steering angle. Fig. 5 shows this structure. In FIG. 5, reference numeral 21 is a high-pass filter to which the steering speed ? _omega is input. Reference numeral 22 is a low-pass filter into which the steering speed _sθh calculated from the steering angle is input. Reference numeral 23 is an adder that sums the output from the high-pass filter 21 and the output from the low-pass filter 22 .

For the structure of FIG. 5 , in the low-frequency region affected by the offset error of the induced voltage EE, the final steering speed θ _hybrid is calculated using the speed obtained from the steering angle θ _h . On the other hand, in the high-frequency region, using The final steering speed θ _hybrid is calculated based on the estimated speed θ _omega of the induced voltage EE. If the transfer coefficient G1 of the high-pass filter 21 is set as G1=Ts/(Ts+1), and the transfer coefficient G2 of the low-pass filter 22 is set as G2=1/(Ts+1), then the structure of Fig. 5 can It is expressed by the following formula (4).

【Mathematical formula 1】

Here, T is a time constant of the cutoff frequency of the high-pass filter 21 and the low-pass filter 22, and s is a Laplacian operator.

In the configuration of FIG. 5 , filtering processing is performed by the high-pass filter 21 in order to eliminate an offset error of the estimated steering speed θ _omega (first steering speed) based on the induced voltage EE. In addition, the cutoff frequency of the high-pass filter 21 is set to a value capable of eliminating offset errors. Therefore, the offset error of the steering speed θ _omega can be eliminated by the filter processing by the high-pass filter 21 . However, when the steering speed is a low frequency below the cutoff frequency of the high-pass filter 21 , the steering speed is canceled together with the offset error, and thus cannot be obtained by the processing of the high-pass filter 21 .

Therefore, in the configuration of FIG. 5, in order to obtain a low-frequency steering speed, the steering speed _sθh (second steering speed ₎ obtained from the steering angle θh is calculated. Thus, the filtering process by the low-pass filter 22 is performed on the steering speed sθ _h obtained only from the steering angle θ _h . The cutoff frequency of the low-pass filter 22 is set to the same value as the cutoff frequency of the high-pass filter 21 . By performing filter processing by the low-pass filter 22, a low-frequency steering speed equal to or less than the cutoff frequency can be obtained.

Thus, the cutoff frequencies of the high-pass filter 21 and the low-pass filter 22 are set to the same value, and the output results from the high-pass filter 21 and the low-pass filter 22 are added by the adder 23 . Thus, when the frequency of the steering angle is higher than the cutoff frequency, the steering speed using the induced voltage EE is used, and on the other hand, when the steering angle is lower than the cutoff frequency, the steering speed using the steering angle _θh can be used. The correct steering speed θ _hybrid is obtained without offset errors.

In addition, the above formula (4) can also be converted equivalently like the following formula (5).

【Mathematical formula 2】

The sum of the estimated steering speed θ _omega based on the induced voltage EE and the value obtained by dividing the steering angle θ _h by the time constant T (θ _omega + θ _h /T) is filtered by the high-pass filter 26 to obtain the final steering Speed θ _hybrid . If Formula (5) is expressed as a block diagram, it will be FIG. 6 . In FIG. 6, reference numeral 24 is a divider that divides the steering angle ? _h by the time constant T. As shown in FIG. Reference numeral 25 is an adder that adds the estimated steering speed θ _omega based on the induced voltage EE to the output of the divider 24 . Reference numeral 26 is a high-pass filter for filtering the output of the adder 25 . T is a time constant of the cutoff frequency of the high-pass filter 22, and s is a Laplacian operator. The transfer function G1 of the high-pass filter 26 is G1=Ts/(Ts+1).

In equation (4), it is necessary to filter the estimated speed θ _omega based on the induced voltage EE by the high-pass filter 21 , and filter the steering speed calculated from the steering angle θ _h by the low-pass filter 22 . Therefore, in the structure of Equation (4) shown in FIG. 5 , it is necessary to perform filtering operations twice.

On the other hand, in the structure of the formula (5) shown in FIG. 6, the calculation can be performed by the primary filtering process, which has the effect of reducing the calculation load.

Next, effects of the second embodiment will be described.

Since the voltage drop voltage Eb of the brush of the motor 6 changes due to influences such as contact oxide films and aging, the induced voltage EE includes these changes as offset errors. Therefore, there is a conventional problem that the estimated steering speed θ _omega based on the induced voltage EE also includes an offset error.

On the other hand, the resolution of the steering angle detected by the steering angle sensor 4 may be low. If the resolution of the steering angle sensor 4 is θ _step and the speed calculation cycle is T _step , the resolution of the steering speed that can be calculated from the steering angle sensor 4 is θ _step /T _step . For example, when the resolution θ _step of the steering angle sensor 4 is 1 deg and the speed calculation cycle T _step is 10 ms, the steering speed resolution is 100 deg/s, which is low as a resolution of the steering speed. In order to improve the resolution of the steering speed, it is considered to set the speed calculation cycle T _step to a large value, or to implement a low-pass filter on the calculated steering speed, but both of them will cause a delay in the response of the steering speed calculation. .

In addition, since the steering angle detected by the steering angle sensor 4 is information obtained via the CAN network, the update cycle may become longer. In this case, the speed calculation period T _step exceeds the update period, and the response of the steering speed calculation will be delayed. That is, there is a problem that the frequency band for speed calculation cannot be increased. As a result, there is a trade-off problem: when the steering speed is calculated from the steering angle sensor 4, if the resolution of the steering speed is increased, the response of the steering speed calculation will be delayed. Conversely, if the responsiveness of the steering speed calculation is increased, the The resolution of the steering speed is reduced.

In Embodiment 2, the steering speed calculation unit 12 can obtain a high steering speed in a frequency band in which an offset is eliminated from the estimated steering speed θ _omega based on the induced voltage EE including an offset error by utilizing the effect of the high-pass filter 21. On the other hand, the effect of the low-pass filter 22 can be used to obtain a high-resolution steering speed with no offset error from the steering angle θ _h . By using both, it is possible to obtain a steering speed with high response and high resolution and with suppressed offset errors.

FIG. 7 shows the results when the cutoff frequency of the high-pass filter 21 and the low-pass filter 22 in FIG. 5 is set to 0.3 Hz. In FIG. 7 , reference numeral 30 is a curve of the steering speed according to the second embodiment, and reference numeral 31 is a curve of the steering speed based on the induced voltage including an offset error. It can be seen from FIG. 7 that the offset influence of the induced voltage EE can be eliminated when the steering speed is near 0, and a good steering speed calculation result can also be obtained for the low frequency region.

As described above, in the second embodiment, the first information on the steering speed is corrected based on the information on the steering angle to obtain the second information on the steering speed. same effect.

In addition, in the second embodiment (the embodiment shown in FIG. 5 ), based on the frequency component extracted from the steering speed information and the frequency component extracted from the first information on the steering speed, the corresponding The second information on steering speed, wherein the steering speed information is calculated based on the information on steering angle, so that a steering speed with high response and high resolution and with suppressed offset error can be obtained. Specifically, in the embodiment shown in FIG. 5 , the steering speed calculation unit 12 calculates the steering speed of the steering system as the second steering speed based on the steering angle θ _h detected by the steering angle sensor 4 , and the second steering speed The value after the low-pass filtering process is used as a correction value, and the value obtained by performing the high-pass filtering process on the estimated steering speed θ _omega (first steering speed) based on the induced voltage EE is added to the correction value, thereby correcting the value based on the induced voltage EE. The estimated steering speed θ _omega of the EE (first information on the steering speed) is corrected and output as the steering speed of the steering system (second information on the steering speed). That is, the high-frequency steering speed in which the offset error is eliminated is obtained from the estimated steering speed θ _omega based on the induced voltage EE including the offset error, and on the other hand, high-resolution without the offset error is obtained from the steering angle θ _h Therefore, by using these two steering speeds, it is possible to obtain a steering speed with high response, high resolution, and suppressed offset error.

In addition, in the second embodiment (the embodiment shown in FIG. 6 ), the low-frequency component of the first information related to the steering speed is corrected based on the above-mentioned information related to the steering angle, so that high response and high resolution can be obtained. rate, and the steering speed at which the offset error is suppressed. Specifically, in the embodiment shown in FIG. 6 , the steering speed calculation unit 12 divides the steering angle θ _h detected by the steering angle sensor 4 by the time constant T (information on the steering angle) as As the correction value, the value obtained by adding the estimated steering speed θ _omega (the first information related to the steering speed) based on the induced voltage EE to the correction value is subjected to high-pass filtering processing, and the obtained value is used as the steering speed of the steering system ( The second information related to the steering speed) is output. That is, the high-frequency steering speed in which the offset error is eliminated is obtained from the estimated steering speed θ _omega based on the induced voltage EE including the offset error, and on the other hand, high-resolution without the offset error is obtained from the steering angle θ _h Therefore, by using these two steering speeds, it is possible to obtain a steering speed with high response, high resolution, and suppressed offset error.

Implementation mode 3.

In the third embodiment, a calculation method different from that in the second embodiment will be described for the calculation of the steering speed performed by the steering speed calculation unit 12 provided in the control unit 11 using the flowchart of FIG. 8 . That is, the flowchart of FIG. 8 is a diagram showing in detail the processing of step S2 of the flowchart of FIG. 3 .

In Embodiment 3, the same reference numerals are used for the configurations common to Embodiments 1 and 2 above, and differences from Embodiments 1 and 2 will be mainly described below. In Embodiment 3, a configuration is adopted in which the steering speed obtained from the induced voltage when the change in the steering angle is small is stored in the memory as a correction value, and the estimated steering speed based on the induced voltage EE is adjusted using the correction value. θ _omega for correction.

FIG. 8 is a flowchart showing the operation of the steering speed calculation unit 12 of the control unit 11 according to the third embodiment. The difference from the flowchart in FIG. 4 shown in Embodiment 2 is that steps S21 and S22 are added in FIG. 8 , and step S23 in FIG. 8 is provided instead of step S14 in FIG. 4 .

In Embodiment 3, first, in step S21, when the control unit 11 can determine that the change in the steering angle obtained by the steering angle sensor 4 is small, it obtains the estimated steering speed θ _omega based on the induced voltage EE, and uses it as The correction value θ _ref is stored in the memory 28 (see FIG. 9 ). The correction value θ _ref will be described below.

When the control unit 11 can judge that the amount of change of the steering angle θ _h obtained by the steering angle sensor 4 is less than the threshold value, that is, when the steering speed θ _h is in the area around 0 (-ε< _θh <ε, ε is an arbitrary number) , and the estimated steering speed θ _omega based on the induced voltage EE at this time is obtained. The calculation method is the same as the calculation method described in the second embodiment. The estimated steering speed θ _omega at this time can be regarded as an offset error from the actual steering speed 0. Therefore, the control unit 11 stores this estimated steering speed θ _omega in the memory 28 as a correction value θ _ref of the steering speed.

Next, the steering speed calculation unit 12 performs the processing of steps S11 to S13 to obtain an estimated steering speed θ _omega based on the induced voltage EE. The processing of steps S11 to S13 is the same as the processing described in Embodiment 2, and therefore description thereof will be omitted here.

Next, in step S22 , the steering speed calculation unit 12 reads out from the memory 28 the correction value θ _ref of the steering speed stored in the memory 28 in step S21 .

Next, in step S23, the steering speed calculation unit 12 corrects the estimated steering speed θ _omega obtained in step S13 by using the correction value θ _ref of the steering speed stored in the memory 28 . Fig. 9 shows this structure. In FIG. 9 , reference numeral 27 is a high-pass filter to which an estimated steering speed θ _omega based on the induced voltage EE is input. Reference numeral 28 is a memory storing a correction value θ _ref of the steering speed. Reference numeral 29 is an adder that subtracts the output from the high-pass filter 27 and the correction value θ _ref of the steering speed read from the memory 28 .

As described above, in the third embodiment, the control unit 11 regards the steering speed obtained from the induced voltage obtained from the steering angle sensor 4 when the change in the steering angle is small as an offset error, and stores it in the memory in advance. 28 in. Thus, the steering speed θ _omega based on the induced voltage EE is corrected using the correcting steering speed θ _ref stored in the memory 28 . Thereby, the offset error can be eliminated, and like the second embodiment, a high-resolution, high-response, and accurate steering speed with the offset error suppressed can be obtained.

In addition, in the above description, it has been described that the estimated steering speed when it is judged that the change in the steering angle θ _h is small is used as the correction value θ _ref of the steering speed.

However, the present invention is not limited to this case, and the steering speed θ _omega based on the induced voltage EE when the steering speed is 0 may be used as the correction value of the steering speed when the system of the steering control device is activated and before the driver turns. θ _ref .

In addition, it is also possible to determine whether or not the change in the steering angle θ _h is small by using detection values of the wheel speed sensor, the yaw rate sensor, and the like. When a wheel speed sensor is used, the wheel speeds of the front and rear wheels are compared, and when the difference is small, it can be determined that the vehicle is traveling straight. When the straight-line running state continues, it can be determined that the steering angle is continuously at 0, so it can be determined that the steering speed is 0. In addition, when a yaw rate sensor is used, changes in the vehicle speed and yaw rate can be used together to determine that the turning state of the vehicle has not changed. Therefore, it can be determined that the steering state is fixed, that is, the steering angle has not changed, and it can be determined that the steering speed is 0.

As described above, in the third embodiment, the first information on the steering speed is corrected based on the information on the steering angle to obtain the second information on the steering speed. same effect.

In addition, in the third embodiment, the first information on the steering speed when the amount of change in the information on the steering angle is smaller than the threshold value is stored in advance as a correction value (information on the steering angle), and based on the correction value (information related to the steering angle) to correct the first information related to the steering speed acquired by the steering speed information acquisition unit, thereby obtaining the second information related to the steering speed, so that the same information as in Embodiment 2 can be obtained. Effect.

Specifically, in the above-described embodiment, it is determined whether the amount of change in the steering angle detected by the steering angle sensor 4 is smaller than a threshold value. The steering speed of the system is stored in advance as a correction value θ _ref , and the correction value is subtracted from the estimated steering speed θ _omega (first steering speed) based on the induced voltage EE when the amount of change in the steering angle is greater than the threshold value. A steering speed is corrected and output as the steering speed of the steering system. That is, in Embodiment 3, it is determined that the steering speed is around 0, and the estimated steering speed θ _omega based on the induced voltage at this time is stored in the memory 28 as the correction value θ _ref , and the correction value θ _ref is used to correct the steering speed based on the steering speed. The estimated steering speed θ _omega of the induced voltage EE when the speed is not near zero is corrected to obtain the same effect as the second embodiment.

Label description

1 steering wheel

2 steering shaft

3 steering wheels

4 Steering angle sensor

5 Torque sensor

6 motors

7 Speed reduction mechanism

8 Vehicle speed sensor

9 Current sensor

10 voltage sensor

11 Control unit

12 Steering speed calculation unit

13 Fixed steering determination unit

14 Target steering speed setting section

15 1st steering assist torque computing unit

16 Steering state judging unit

17 Second steering assist torque computing unit

18 Addition Department

19 Current Driver

Claims (6)

1. A steering control device, characterized in that, including electric motors that provide steering assist torque to the vehicle's steering system, The steering control device includes: a steering angle information acquisition unit, the steering angle information acquisition unit detects the steering angle of the steering system; a steering speed information acquisition unit that estimates a steering speed from an induced voltage of the electric motor and outputs it as an estimated steering speed; and a correction unit that calculates a steering speed based on the steering angle detected by the steering angle information acquisition unit, uses a value obtained by performing low-pass filter processing on the steering speed as a correction value, and adjusts the steering speed to adding a high-frequency component of the estimated steering speed acquired by the speed information acquiring unit to the correction value after performing high-pass filter processing on the estimated steering speed, thereby correcting a low-frequency component of the estimated steering speed, And output it as the steering speed of the steering system. 2. A steering control device, characterized in that, including electric motors that provide steering assist torque to the vehicle's steering system, The steering control device includes: a steering angle information acquisition unit, the steering angle information acquisition unit detects the steering angle of the steering system; a steering speed information acquisition unit that estimates a steering speed from an induced voltage of the electric motor and outputs it as an estimated steering speed; and a correction unit that divides the steering angle acquired by the steering angle information acquisition unit by a time constant of a cutoff frequency of a high-pass filter as a correction value, and converts the steering speed information acquisition unit to A value obtained by adding and correcting the acquired estimated steering speed to the correction value is subjected to high-pass filter processing, and the value after the high-pass filter processing is output as a steering speed of the steering system. 3. The steering control device according to claim 1 or 2, further comprising a first steering assist torque calculation unit based on the steering torque output from the correction unit. The deviation between the steering speed of the system and the target steering speed is used to calculate the steering assist torque. 4. A steering speed detection method, characterized in that, comprising: Steering angle information acquisition step, the steering angle information acquisition step uses a steering angle sensor to detect the steering angle of the steering system of the vehicle; a steering speed information acquisition step of obtaining a motor rotation speed from an induced voltage of a motor that provides steering assist torque to a steering system of the vehicle, estimating the steering speed from the motor rotation speed, and using it as the estimated Steering speed for output; and a correction step of obtaining a steering speed based on the steering angle detected in the steering angle information obtaining step, using a value obtained by low-pass filtering the steering speed as a correction value, and converting the The high-frequency component of the estimated steering speed obtained by performing high-pass filter processing on the estimated steering speed obtained in the steering speed information obtaining step is added to the correction value, thereby reducing the low-frequency component of the estimated steering speed Correction is performed and output as the steering speed of the steering system. 5. A steering speed detection method, characterized in that, comprising: Steering angle information acquisition step, the steering angle information acquisition step uses a steering angle sensor to detect the steering angle of the steering system of the vehicle; a steering speed information acquiring step of obtaining a motor rotational speed from an induced voltage of a motor provided in a steering system of the vehicle to provide steering assist torque to the steering system, and estimating the steering from the motor rotational speed speed and output it as estimated steering speed; and a correction step of dividing the steering angle detected in the steering angle information obtaining step by a time constant of a cutoff frequency of a high-pass filter as a correction value, and converting the steering speed information obtaining step to The estimated steering speed obtained by adding and correcting the correction value is subjected to high-pass filter processing, and the value after the high-pass filter processing is output as the steering speed of the steering system. . 6. The steering speed detection method according to claim 4 or 5, further comprising a first steering assist torque calculating step based on the output of the correcting step The steering assist torque is calculated based on a deviation between a steering speed of the steering system and a target steering speed.